Process for conducting catalytic reactions



May 4, 1948.

K. H. HACHMUTH PROCESS FOR CONDUCTING CATALYTIOREACTIONS Filed may '7, 1940 INVENTOR KARL H. HACHMUTH BY ai: l L "1:4 7 l g l ATTORNEY Patented May '4, 194s PROCESS FOR CONDUCTING CATALYTIC REACTIONS Karl H. llachmuth, Bartlesville, Okla., assignor to Phillips Petroleum Company, acorporation i of Delaware Application May 7, 1940, Serial No. 333,872

This invention relates to the conducting of catalytic reactions and more particularly to the conducting of a catalytic reaction within an elevated temperature range with two or more portions of a catalyst that are used in parallel and that diier in activity.

In the conducting of a catalytic reaction to obtain a profitable rat of reaction with a given body of catalyst, the operating conditions generally must be progressively changed to compensate for decrease in catalytic activity as the catalyst gradually becomes deactivated. Usually the most convenient compensatory change is a gradual increase in the reaction temperature. Final1yhowever, the catalyst is so fully reactivated that any further increase in temperature is unprofltable or is otherwise undesirable. At this point the catalyst is replaced, or it isv reviviiied by a procedure that removes the deactivating material deposited on it during use. When only one portion of catalyst is used at a time, the replacement or the reviviiication causes an undesirable interruption of the catalytic reaction; for this-reason, two or more portions of catalyst, generally within individual catalyst chambers, are preferably used. These'portions become fully deactivated one by one in turn, Vat approximately equal intervals of time, and each is replaced by fresh or revivied catalyst without interrupting the conversion occurring in the other portions. During use of such a multiplicity of portions orf catalyst, the catalytic reaction or conversion must be effected at different temperatures in the various portions, in accordance with the different degrees of catalytic activity, in order that' each portion may effect its share of the aggregate conversion.

In the past, the different temperatures required in the various portions of catalyst have been obtained by separatelyheatlng each portion or body of catalyst, or, the stream of reactant material coming into contact therewith, to the proper temperature; this system entails the use of a separate heating unit for each portion of catalyst, and each unit must be continuously adjusted to provide the temperature required at the moment. lSuch a system of a multiplicity of heating units,` which may be separate sections of a common heater or individual heaters, one for each portion of catalyst, suffers from` the disadvantages of 'complexity both inthe amount of the heating equipment and in its operation.

In one modication, the present invention comprises the steps of dividing` a stream of ma- 12 Claims. (Cl. 260683.15)

terial. which is -to undergo a catalytic: reaction, into a least two substreams; heating one of the substreams to at least about the maximum temperature at which the reaction is to be effected, any effect of the reaction itself upon the temperature being disregarded, or to about the maximum temperature desired for the charge stock for the reaction; and forming from thehot substream and the coolersubstream a multiplicity of reactant streams equal in number to a multiplicity of portions or bodies of a catalyst that are used simultaneously in separate catalyst zones for effecting said catalytic reaction, eachof said reactant streams being formed of such proportions of the heated and the unheated substreams that the temperature of the resultant stream corresponds to the instantaneous degree of activity of the body of catalyst with which it is to be in contact, in such a way that each of the reactant streams undergoes a predetermined degree of conversion during its period of contact with the catalyst.

One of the objects of the invention is to provide a process of obtaining diierent reaction temperatures in two or more separate catalytic reaction zones, arranged in parallel and provided with portions of catalyst or with different catalysts for the same reaction, that differ in activity,

`in such a manner that each zone or portion effects a predetermined share of the aggregate conversion.

Another object is to effect by means of a single y heating unit, the establishment of different temperatures in two or more parallel streams of re- `actant material that subsequently pass into contact with separate portions of a catalyst that have diierent instantaneous degrees of catalytic activity.

Still another object oi' the invention is to use a single heating unit to provide a heat-carrying material to two or more reaction zones which are maintained at diierent temperatures.

A further object of my invention is to obtain, from a single charge stream and a single heating unit, two or more charge streams of different and independently variable temperatures.

Another object of the invention is to provide ,a means for 'continuously blending two separate streams to forma composite stream with desired characteristics. v

Other objects and advantages of the invention will be obvious to those skilled in the art.

'I'he invention may be used for the conduction of any process which involves a catalytic reaction that requires a temperature differing from atmospheric temperature and it may be used in connection with either an endothermic or an exothermic reaction. Although the in vention will generally be practiced in connection with reactions at elevated temperatures, it may be readily applied to reactions carried out at low temperatures by cooling one of the substreams. It is especially valuable for conducting catalytic reactions involving hydrocarbons either as reactants or as products, such as hydrogenation, dehydrogenatlon, polymerization, depolymerization, alkylation, cracking, desulfurization, oxidation, hydration, dehydration (suchl as of alcohols to oleilns), -and'the like; but it may be used also for conducting catalytic reactions in which hydrocarbons are not involved.

Numerous methods may be employed for blending portions of the hot and of cooler substreams to form a charge stream having a desired temperature for any particular catalyst chamber.

In a modification which may be often used,

branch pipes, each controlled by an individual valve, are led from a hot-stream manifold and a cold-stream manifold, respectively, one branch from each manifold comprising the feed to a catalyst chamber. If desired, the valves on each such branch may be so interconnected, or otherwise controlled, that as one is opened the other .is closed and the composite stream can vthus readily be varied as to temperature without appreciable variation in total volume, when a substantially constant total volume is to be used. However, I have found that ow control valves do not generally operate entirely trouble-free on hot streams, and have developed other and novel means for controlling the streams. In such a novel modication, the rate of flow of the composite stream is controlled or limited by suitable flow control means, or is maintained at the maximum capacity of the pipe or conduit through which it flows, and a :dow-control valve on the cooler stream is actuated by a temperature responsive deviceno control valve being used on the hot stream. The flow of the hot stream is thus controlled indirectly,` without the direct use of a separate valve, by the cooperation of the actions of the limitation of ow of the composite stream and the ow control of the cooler stream.

Solely for the sake of simplicity, it being understood that the invention is not to be limited thereby, an application of 'my invention will be described in connection with the conduction of the polymerization of oleilns at elevated temperatures, such as the polymerization of normally gaseous oleilns to gasoline-range hydrocarbons.

The accompanying drawing is a dow-diagram illustrating diagrammatically a specic embodi-4 ment of the invention as applied to such a polymerization. Substantially the same arrangement zn be used in a dehydrogenation process, or the The feed, comprising polymerizable olellns, enters the system through inlet I and pump 2, which maintains it at any desired pressure. It is divided into two substreams, one of which is hea-ted to a desired temperature in heating coil 3 in heater 4, and the other of which passes unheated, or only partially heated as by indirect heat exchange with the catalyst eiiiuent 31 (not shown) or by heat exchange in the economizer section of a furnace 4A, through conduit 5. The temperature to which the rst substream is heated generally is at least as high as the maxi- '4 mum temperature desired for the charge stock to the polymerization step in the presence of the least active catalyst body that is to be used in the subsequent polymerization chambers; in addition, the temperature should be high enough to compensate for any heat loss occurring prior to the polymerization. A temperature of about 450 to 600 F. is suitable for most purposes,- but it maybe higher or lower than this value in particular instances. The temperature is preferably maintained at a substantially constant level by means ot an automatic temperature controller,

not shown, that regulates the inputof heat or of fuel to heater 4.

Although generally coil 3 is so constructed that the pressure drop in it and conduit 6, taken together, is greater than that in conduit 5, at times it may be desirable to increase the resistance to flow oi the heated substream. Such an increase may be readily eiected by constricting this substream. as by control-valve 3| or by a constriction in conduit 6.

The hot substream passes from heater 4 through conduit and manifold 6, from which lead branch pipes 1, 8, 9, I9. The cooler substream passes through valve 45 and conduit and manii'old 6, from which lead branch pipes II, I2, I3, and I4. Branch pipes, 1, 8, 9, and I 0 are Joined to II, I2, I3, and I4, respectively, and from their junctures pipes I9, 20, 2|, and 22 lead to catalyst chambers 23, 24, 25, and 26, respectively. The rates of ilow through pipes I9, 20', 2I, and 22 are preferably controlled by flow-control valves 21, 28, 29, and 39. respectively, and are generally held substantially constant for long, periods of time. This ilow control is adapted to set a maximum on the total ilow, more than suillcient material being available to supply this maximum. In some instances the capacity of any one of the pipes I9 to 22 may be a suillcient limit and maximum, so that no additional control is necessary.

In most cases, however, it will be desirable at times not to reach the capacity of the pipe carrying the combined streams as a maximum and for this reason some sort of now-control, as shown, will be used. These flow-control valves may be manually or otherwise operated, as desired, but very satisfactory operation is obtained by having them automatically controlled through the agency of means actuated by an orice flow meter, or other type o! ow meter, represented by 21', 29', 29', and 30', respectively. The individual regulating means may all be set to the same flow rate, orto different flow rates, as individual circumstances may indicate is desirable or necessary. The temperatures of the composite streams owing through each of the pipes I 9, 20, and v2|, and 22 are regulated by flow-control valves I5, I6, I1, and I9 in branch pipes II, I2, I3, and I4, respectively, which convey the cooler material. These valves may be manually or otherwise operated, as desired, but I have obtained good performance by having them actuated by temperature responsive devices or means which respond to the temperatures of the composite streams in conduits I9, 20, 2|, and 22, as represented by I5', I6', I1', and I9', respectively. With this arrangement, a slight positive differential is maintained in manifold 5 over that in manifold 6, thereby insuring a positive iiow through the control valves I5, I6, I'I, and I8 at all times. The temperature responsive devices should be placed at a suillcient distance from the union of the hot and cooler streams to result in aurate control. such as at a suillcient distance to insure effective mixing of the streams. Other means for accomplishing the same result may be used, but for most' applications this arrangement is the simplest. A number of automatic controllers, or similar means, are available commercially, and can be readily' adapted by one skilled in the art. Such may be set to any desired temperature or temperatures for the composite streams, and will then operate the flow control valves I5 to I8 to maintain such temperatures. Such temperature values may be changed from time to time as desired, either by hand or automatically, as referred to hereinafter.

In catalyst chambers 23, 24, 25, and 26, polymerization of oleflns to heavier hydrocarbons ls effected in the presence of a polymerization catalyst. Each catalyst chamber generally contains a different portion or body of the same cataly-tic material, and in general at any particular moment the diiferent bodies of catalyst have different degrees of activity and hence require different temperatures, all other conditions being -the same, to eilect substantially the same predetermined extent of polymerization. With this particular modification these different temperatures are obtained by suitable control of valves I5, I6, I1, and I8. As the catalyst body in any particular catalyst chamber becomes progressively deactivated, the temperature of the incoming reactant stream must be correspondingly increased to effect the same extent of conversion. This increase may be effected by a manual setting of the corresponding automatic controller actuating the appropriate valve of the valves I5, I6, I'I, or I8 so that less unheated material passes through the valve controlled by the automatic controller. Alternatively, the setting of such an automatic controller may be changed by a secondary automatic controller that is responsive, directly or indirectly, to the extent of polymerization effected by the corresponding catalyst body; that is, the secondary controller (not shown) being actuated by some characteristic of the effluent streams in the appropriate conduit 23, 24', 25', or 26', respectively, leading from one of the catalyst chambers 23, 24, 25, or 26, and so setting or controlling the primary controller I5', I6', I'I', or I6' that the temperature in the reactant stream is adjusted to `that required to effect a definite predetermined degree or extent of polymerization. For example, the secondary controller may be made responsive to the change in composition of the efiluent stream that leaves the catalyst chamber, or to the change in temperature that takes place between inlet and eiiluent streams as a result of the polymerization, which is an exothermic reaction. Since sufllcient ma-` terial-is available to maintain the maximum flow through any one of the pipes I 9 to 22 at all times, a decrease in the cooler stream automatically results in a rise in temperature of the composite stream Without changing the total flow rate, and the converse is also readily obtained.

Although no restriction as to the size of the l various portions or bodies of catalyst, or of the various reactant streams, is necessary for the operation of the invention, it is generally preferred to useportions of substantially equal size and to make the reactant streams also substantially equal in size. However, at times the reactant streams may be advantageously made different in size; thus if one or more of the catalyst bodies is different from the rest as to size, a corresponding difference may be maintained for the reactant stream, or one or more o! the streams may be made'relatively disproportionate to the size oi the portion of catalyst with which it comes into contact if catalyst bodies of equal size are used. For example, at times improved results may be obtained with a relatively less active, or a relatively deactivated catalyst portion by a rate of ilow lower thanthat used for the other catalyst portions. Such a relatively low rate tends to decrease the temperature required. to increase the quality of the product, and to prolong the period of use of the'catalyst portion by decreasing its rate of deactivation. Conversely, if it is desired to hasten the deactivation of a particular catalyst portion, Vin order that its removal from the process upon deactivation shall occur ata predetermined time, the rate of flow may be made relatively large. y

Regardless of the requirements in any particular case, the preferred arrangement of control valves shown is so flexible that they can be met. By its use, individual operation of each catalyst chamber in any desired manner can be obtained within broad limits of pressure, temperature, and

rate of ilow, independentlyof the manner of operation of the 'other catalystv chambers, and any chamber may be removed from the system or other chambers may be introduced as will be` appreciated.

After the polymerization has been elected.` in catalyst chambers 23, 24, 25, and 26, the various streams of products pass through gate valves 32, 33, 34, and 35, respectively, and are combined. The resulting composite effluent stream passes through control valve 36, which serves as a pressure reduction valve, and conduit 31 to fractionator 38, in which fractionation is eiected into at least two fractions, such as a fraction containing the desired polymer product, which may be withdrawn from the 'system through valve 39 and outlet 40, and relatively light or unreacted hydrocarbons, which may be withdrawn through valve 4I and outlet 42, which may be treated in whole or in part to increase the concentration ofolens, as by dehydrogenation, and then reprocessed. l

Although the substream 5 has been primarily described as an unheated stream, it may be heated to a certain extent, preferably not above the minimum temperature desired for any particular reactant stream. This partial heating of substream 5 may be accomplished by any desirable or available means, as by indirect heat exchange with the catalyst eilluent or by heat exchange in the economizer section of a furnace 4A, thereby utilizing waste heat and reducingthe heat input of heater 4.. In case two separate streams are available, one may be heated as discussed and the other introduced `in an unheated condition through pipe 44, with valve 45 in pipe 5 partially or completely closed, as may be desired. In a catalytic cracking or dehydrogenation process, for example, the heated stream vmay comprise recycled unreacted material while the unheated` stream may comprise fresh charge stock. The hot stream may be subjected to Example I A feed having the following molfpercentage composition was used as charge to a catalytic polymerization operation:

This feed was pumped to a pressure somewhat exceeding 1500 pounds per square inch; its temperature was about 100 l'f. Part of the feed stream was heated to a temperature of about 600 F. in a tube coil heated by the burning of fuel gas. The temperature of the heated stream was maintained substantially constant by an automatic controller that regulated the amount of fuel gas being burned. Passage of this part of the feed stream through the tube coil caused its pressure to decrease to about 1500 pounds per square inch. The other part of the feed stream was not heated.

Four catalyst chambers of equal size were used, all containing substantially equal amounts of a solid, granular silica-alumina polymerization catalyst comprising alumina adsorbed on silica gel similar to that described in McKinney Patent No. 2,142,324. However, only three of the cham-V bers were used at a time, the fourth being ready to be used in its turn upon deactivation of one of the three. That is, the fourth chamber was conditioned for use during operation of the other three, as by reviviflcation of spent catalyst or by replacement of spent catalyst with fresh catalyst, and was put into operation when a chamber containing deactivated catalyst was withdrawn from operation.

Because, at any particular moment, the bodies of catalyst in the three catalyst chambers in simultaneous use had been in service for different periods, they had different degrees of activity and therefore required different temperatures to effect the same extent of polymerization. At first. when fresh, a portion of catalyst required a temperature of about 220 F. in the incoming reactant stream in order to effect polymerization to the extent that the normally gaseous hydrocarbons in the eilluent from the catalyst chamber had a mol-percentage composition approximately as follows:

Ethylene Ethane 0.35 Propylene e 5.53 Propane 8.11 Butylenes 1.63 Butanes 83.78

The extent of polymerization was 18.8 per cent by weight of the feed. As each catalyst body underwent progressive deactivation, the temperature had to be correspondingly increased, in order for the extent of polymerization to be maintained. Finally, when the temperature of the incoming reactant stream reached 450 F., the body of catalyst was considered sufllciently deactivated to be removed from service and replaced by a fresh or a revivied body of catalyst. The catalyst used was capable of polymerizing at a' satisfactoryl ratev up to a `temperature of about 600 F., but the proportion of Polymers heavier than the dimer in the product tended to increase at temperatures about about 450 F., which was undesirable for the present operation.

The catalyst chambers were not'heated other` wise than by the reactant streams. The chambers were insulated against excessive heat loss; what heat loss occurred was more' than com.- pensated by exothermic heat of polymerization, which in addition caused the temperature of the eilluent to be about to 90 F. above that of the incoming reactant stream.

Each of the three reactant streams going into the three catalyst chambers insimultaneous use was formed from both the feed stream heated to about 600 F. and the unheated feed 'stream at about 100 F. An automatic controller, actuated by a thermocouple located in the -reactant stream at the inlet oi the catalyst chamber, adjusted a valve controlling the addition of the unheated material to the heated material going to the chamber; that is, this controller so increased or decreased the cold feed to the chamber that the temperature of the composite, reactant stream was substantially constant at the value necessary at the moment for the'desired extent of polymerization to be effected. From time to time. as the catalyst progressively became deactivated, the setting of the controller was manually changed, so that the temperature of the reacting stream was correspondingly increased and the extent of polymerization was maintained at substantially the same level until finally' the body of catalyst Was so deactivated las to require replace ment or revivification.

An automatic now controller, actuated by an orifice flow meter through which the reactant stream passed just before reaching the catalyst chamber, controlled the rate ofvfiow of the composite reactant stream by automatically adjusting a flow-control valve,`through which the com posite reactant stream passed, in such a way as to compensate for fluctuations in the pressure and in the backpressurefdeveloped in the catalyst chamber.

The extent of polymerization in each individual catalyst chamber was followed by weathering cc. samples of the eilluent, Withdrawn from the outlet of the chamber through a small cooling coil immersed in an ice bath. After the Weathering, which took place at atmospheric pressure, the amount of residue remaining at 100 F. indicated qualitatively the extent of polymerization, and the temperatures in the individual chambers were adjusted until all gave the same amount of residue. Periodicdeterminations of the butylene content ofthe eiliuent indicated quantitatively the thoroughness of the polymerization. If too much butylene was present in the eilluent, the temperatures in all three chambers were increased; later, small adjustvments were made individually to bring the cham- Example II In another polymerization process a total of five catalyst chambers were used. four being on- Component st.. Estf Pro Iene g 3. 07 3. 39 Progne... ll. 38 l2. 65 Butylenes.. 18. 75 2.07 Butaues... 06. 80 73. 52 Polymer 0. 8. 47

In this sample, the temperature and the rate of flow of each of the `four reactant streams were controlled and adjusted substantially in the manner described in Example I.

Although in the foregoing two examples the operating pressure was about 1500 pounds per square inch. it will be recognized by those skilled in the art that pressures above and below this value can be used in the polymerization processes described. As is well known, almost any pressure can be used in a catalytic polymerization process, but high pressures within the range of 500 to 2000 pounds per square inch are preferred to low pressures on thermodynamical grounds and on the grounds of eflicient handling of materials.

The use of a plurality oi' catalyst chambers having catalyst portions of different instantaneous degrees of activity. and the use of diierent temperatures obtained in the manner described, results in an evening-out of the heat load on the fractionating system -that fractionates the eiiiuent from the catalyst chambers. This advantage becomes the greater, the larger the number of catalyst chambers; for, with an increase in this number, the disturbance ln heat load resulting from the replacement of a spent portion of catalyst by .a fresh portion becomes relatively smaller. However, a number within the range of three to six is usually adequate, and therefore such a number is preferred.

Many modifications and variations of this invention may obviously be used, and can be adapted by one skilled in the art without departing from the spirit of the disclosure. 'I'he restrictions used in the examples, and in connection with the drawing. need not necessarily be used as limits for all particular operations or sets of conditions, since they are presented primarily as illustrative examples. It will be understood that the-flow diagram presented and described as a part of the disclosure is schematic only, and that many additional conventional pieces of equipment, such as pressure gauges, valves, pumps, heat exchangers, reflux lines and accumulators, heaters and coolers, and the like, will be necessary for any particular installation, and can be supplied to meet the requirements of any particular case by anyone skilled in the art. The essential equipment and conditions have beenv described and the modications discussed in sumcient detail to serve as eilicient guides. Although catalytic cracking and dehydrogenation operations are endothermic rather than exothermic. the fundamentals oi.' my

action in the presence of a catalyst that progressively decreases in catalytic activity with use in a plurality of catalytic reaction zonesoperated in parallel in such manner that substantially the same extent ofconversionis eiiected in each said. y catalytic reactionzona and the Vextentbf conversion is maintained substantially constant throughout the entire period of operation, the improvement which comprises separately passing to each said catalytic reaction zone a portion of a heated stream of the charge stock and :a portion of a cooler` stream of the same charge stock, the relative portions of the two streams being individually regulated for each of said zones and being such that substantially the same extent of conversion is eiected in each said zone and thereafter, while maintaining the rate of iiow oi the total charge to each said catalytic reaction zone substantially constant. progressively raising the temperature of the total charge stock to each said catalytic reaction zone, as the catalyst progressively decreases in activity, by progressively decreasing the proportion of the cooler stream and increasing the proportion of the heated stream that is charged to said catalytic reaction zone.

2. In a process for the catalytic conversion of a low-boiling oleiin hydrocarbon in the presence of a solid conversion catalyst that progressively decreases in catalytic activity with use to form a higher-boiling hydrocarbon in a plurality of catalytic reaction zones operatedin parallel in such manner that substantially the same extent of conversion is eiIected in each said catalytic reaction zone and the extent of conversion is ymaintained substantially constant throughout the entire period of operation, the improvement which comprises separately passing to each said conversion zone a portion of a heated stream of the olefin charge stock and a portion of a cooler streamof the same charge stock, the relative portions of the two streams being individually regulated for each of said zones and being such that substantially the same extent of conversion is effected in each of said zones and thereafter. while maintaining the rate of flow of the total charge to each said catalytic reactionzone substantially constant, progressively raising the temperature of the total charge stock to each said catalytic reaction zone, as the catalyst therein progressively decreases inactivity, by progressively decreasing the proportion of the cooler stream and increasing the proportion of the heated stream that is charged to said catalytic reaction zone.

3. A process as deiined in claim 2 in which the solid conversion catalyst comprises a granular catalyst of the silica-alumina type.

4. A process as defined in claim 2 in which the polymerization is effected ata pressure within the range of approximately 500 to approximately 2000 pounds per square inch.

5. A process as dened in claim 2 in which the low-boiling olefin hydrocarbon is a butylenie.

6. A process as dened in claim 2 in which the temperatures of the mixed oleiin hydrocarbon 11 stocks that are charged to the catalytic reaction zones are within the range of approximately 220 to approximately7 450 F.

7. In a process for the catalytic polymerization of olen hydrocarbons in a plurality of polymerization chambers operated in parallel, and containing a solid granular polymerizaiton catalyst that progressively decreases in catalytic activity with use, in such manner that substantially the same extent of conversion is effected in each said polymerization chamber and the extent of conversion is maintained substantially constant throughout the entire period of operation, the improvement which comprises dividing the stream comprising the polymerizable oleiins into two substreams, heating one of the substreams to approximately the maximum temperature at which the polymerization is to be effected, forming from the heated substream and the unheated substream a plurality of reactant streams, each of said reactant streams being individually formed of such proportions of the heated and the unheated substreams that the temperature thereof corresponds to the concurrent degree of activity of the body of polymerization catalyst with which it is to be contacted, in such manner that each of the reactant streams undergoes substantially the same degree of polymerization during its period of contact with the catalyst, passing each said reactant stream to its corresponding polymerization chamber, and thereafter, while maintaining the rate of flow of the total charge to each said catalytic reaction zone substantially constant, progressively raising the temperature of the total charge stock to each said catalytic reaction zone, as the catalyst therein progressively decreases in activity, by progressively decreasing the portion of the cooler stream and increasing the proportion of the heated stream that is charged to said catalytic reaction zone.

8. A process for the catalytic polymerization of an oleiin hydrocarbon mixture comprising propylene and butylenes in a plurality of catalytic polymerization zones operated in parallel and in the presence of a silica-alumina catalyst that progressively decreases in catalytic activity with use, which comprises separately passing to each said catalytic reaction zone a portion of a stream of the olefin hydrocarbon mixture comprising 'propylene and butylenes that is heated to a temperature of approximately 600 F. and a portion of a cooler stream of the same olefin hydrocarbon mixture that is at a temperature of approximately 100 F., the --relative portions of the two streams being individually regulated for each of said zones and being such that substantially the same extent of polymerization is eiected in each of said zones and the temperature of the streams entering said zone is within the range of approximately 220 F. to approximately 450 F. andthereafter, while maintaining the rate of flow of the total charge to each said catalytic polymerization zone substantially constant, progressively raising the temperature of the total charge stock to each of said catalytic reaction zones, as the catalyst therein progressively decreases in activity, by progressively decreasing the proportion of the cooler stream and increasing the proportion of the heated stream that is charged to said catalytic polymerization zone, and subsequently discontinuing the operation of a particular catalytic polymerization zone when the temperature of the stock charged to said zone is approximately 450 F.

9. In a process for the catalytic dehydrogena- 12 tion of a hydrocarbon to form hydrogen and hydrocarbons ofy lesser degrees of saturation in the presence of a solid dehydrogenation catalyst that progressively decreases in catalytic activity with use and in a plurality of catalytic dehydrogenation zones operated in parallel in such manner that substantially the same concentration of hydrocarbons of lesser degrees of saturation is present in the eiiluent of each said catalytic dehydrogenation zone and this concentration is maintained substantially constant throughout the entire period of operation, the improvement which comprises heating a rst stream of the hydrocarbon to be dehydrogenated to approximately the maximum temperature at which the dehydrogenation is to be eiected, passing a portion of said heated stream to each o f said plurality of catalytic dehydrogenation zones, admixing with each said portion of said heated stream a portion of a second cooler stream of a hydrocarbon to be dehydrogenated in such relative amount that the resultant eliiuent stream of ing the proportion of the heated stream that is l charged to said catalytic reaction zone.

10. In a process for the catalytic dehydrogenation of a hydrocarbon to form hydrogen and hydrocarbons of lesser degrees o t saturation in the presence of a solid dehydrogenation catalyst that progressively decreases in catalytic activity with use and in a plurality of catalytic dehydrogenation zones operated in parallel in such manner that substantially the same concentration of hydrocarbons of lesser degrees of saturation is present in the eilluent of each said catalytic dehydrogenation zone and this concentration is maintained substantially constant throughout the entire period of operation, the improvement which comprises heating a iirst stream consisting of the hydrocarbon to be dehydrogenated together with recycle hydrocarbon material from the process to approximately the maximum temperature atr which the dehydrogenation is to be effected, passing a portion of said heated stream to each of said plurality of catalytic dehydrogenation zones, admixing with each said portion of said heated stream a portion of a second cooler stream of the hydrocarbon to be dehydrogenated in such relative amount that the resultant eflluent stream of material passing from each said catalytic dehydrogenation zone has substantially the same content of hydrocarbons of lesser degrees of saturation, said admixing being effected independently for each of said zones, and thereafter, while maintaining the rate of iiow of the total charge to each of said catalytic reaction zones substantially constant, progressively raising the temperature of the total charge stock to each said cata- Vcatalyst decreasing as the processing period progresses, the catalyst being periodically regenerated to restore its activity, and the operation being made continuous by employing a plurality of reaction zones in which the catalyst is disposed, each of said reactionV zones being alternately processed Aand regenerated and wherein the conversion reaction is conducted Vsimultaneously in at least two of said reaction zones and the time of introduction of the hydrocarbon reactants is so regulated that said reaction zones are in different stages of processing, the improvement which comprises, heating separate streams of the hydrocarbon reactants each to a different temperature, supplying to the reaction zones as the conversion reaction progresses therein varying portions of said separately heated streams, said portions being regulated to maintain a high space velocity and relatively low temperature in the reaction zone wherein the catalyst activity is relatively high, and to maintain a lower space velocity and high temperature in the reaction zone wherein the catalyst activity is relatively low.

12. In the process of catalytically cracking hydrocarbons wherein the hydrocarbon reactants are heated to reaction temperature and passed in contact with an active catalyst capable l of promoting the reaction, the activity of said catalyst decreasing as the processing period progresses, the catalyst being periodically regenerated to restore its activity, and the operation ybeing made continuous by employinga Iplurality of reaction zones in which the catalyst is disposed, each of said reaction zones being all ternately processed and regenerated and wherein the conversion reaction is conducted simultaneously in at least two of said reaction zones and the time of introduction of the hydrocarbon reactants is so regulated that said reaction zones are in different stages of processing, the improvement which comprises, heating separate streams of the hydrocarbon reactants each to a different temperature, supplying to the reaction zones as the conversion reaction progresses therein varying portions of said separately heated streams. said portions being regulated to maintain a high space velocity and relatively low temperature in the reaction zone wherein the catalyst activity is relatively high and to maintain a lower space velocity and high temperature in the reaction zone wherein the catalyst activity is relativelyA low.

KARL H. HACHMU'I'H.

REFERENCES CITED The following references are of record in the le of this patent:

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